1. Field of the Invention
The present invention relates to etching processes, and more particularly, to a process for etching ruthenium using an oxygen plasma.
2. Discussion of the Prior Art
The use of plasma etching techniques to define features in the fabrication of printed circuits, including semiconductor integrated circuits, is generally known. Plasma etching is highly desirable because it etches anisotropically and therefore achieves high definition of fine lines and features. However, plasma etching has been used primarily to etch refractory metals, such as aluminum, tungsten, or titanium. See, for example, U.S. Pat. No. 3,923,569. Further, the only type of plasmas which have been effective to anistropically etch refractory metals are limited to some combination of chlorinated or fluorinated gas.
The use of ferroelectric materials to fabricate integrated circuit memory cells is also generally known. However, it is critical in such fabrications that the ferroelectric material be prevented from interacting with other features of the circuit, such as the refractory metals which are used to form interconnects or other conductive features. Ruthenium has been found to be an effective barrier to prevent interaction of refractory metal with ferroelectric material. However, the only effective known method of etching ruthenium involves sputter etching after patterning a hard mask, and this is a slow and expensive process step.
Thus, it would be desirable if ruthenium could be etched with high definition in a simple and quick processing step.